At the beginning of the WWII on 01 September 1939 the Wehrmacht was equipped with 11.200 anti tank guns 3,7 cm Pak 35/36 that could effectively fight Polish and Soviet light tanks of the early period with their light anti bullet armor, however it couldn’t penetrate medium tanks such as British Matilda and Russian T-34 and KVs which resulted in the nickname “Door Knocker” by the Germans.